Apparatus and a method for controlling a priority access and channel assignment call in a mobile telecommunication system

ABSTRACT

Disclosed is a method for controlling a PACA call in a mobile telecommunications system, which comprises: sending a new origination message from a mobile station in a PACA state to a base station; sending a service request message for a PACA call from the base station to a mobile switching center, requesting from the mobile switching center the base station to assign a traffic channel to the mobile station; assigning an available traffic channel to the mobile station to start a communication; and distinguishing the PACA call service from an ordinary call service.

PRIORITY

[0001] This application claims priority to an application entitled“Method for Controlling a Priority Access and Channel Assignment Call ina Mobile Telecommunications System” filed in the Korean IndustrialProperty Office on Jun. 1, 2000 and assigned Serial No. 2000-30012, thecontents of which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to a mobile telecommunicationsystem, and more particularly to an apparatus and a method forcontrolling a priority access and channel assignment call in a mobiletelecommunication system.

[0004] 2. Description of the Related Art

[0005] Generally, the priority access and channel assignment (PACA) callis a channel assignment service provided to a subscriber. PACA allows asubscriber to obtain communication priority, so that when a userrequests a base station (BS) make a call to a mobile station that ispresently not available because its traffic channel is receiving toomuch traffic then the mobile station (MS) switches to a standby mode sothat it may be assigned to the traffic channel when the traffic channelis idle and available. Here, the standby mode of the MS is defined asthe “PACA state”, which is described in connection with FIGS. 1 and 2.

[0006] Referring to FIG. 1 there is illustrated a schematic diagram of aconventional mobile telecommunication system. It consists of a PublicSwitch Telecommunications Network (PSTN) 160, a Public Land MobileNetwork (PLMN) 150, a mobile switching center (MSC) 130, a home locationregister (HLR) 140, a base station controller (BSC) 120, abase station(BS) 110, and an MS 100. MS 100 communicates with both PSTN 160 and PLMN150. The BSC 120 performs both wired and wireless link control andhand-off. The BS 110 provides the wireless traffic channel to MS 100,which manages wireless traffic resources. The HLR 140 registers thesubscriber's location, although, not shown, the visitor locationregister (VLR) does the same function.

[0007] In FIG. 2, there is illustrated a flow diagram that depicts aconventional process for shifting the MS to the PACA state. MS 100 isrequested by the user to send a signal in step 211. If MS 100 does notrequest a signal be sent, then the signal stays at MS 100. In step 213,if MS 100 requests a signal be sent, MS 100 transmits an originationmessage to BS 110. BS 110 sends the signal as a call service requestmessage “CM_SERVICE,” REQ to MSC 130, in step 215. Then, if MSC 130sends an assign request message, “ASSIGN REQ” to BS 110 to assign atraffic channel for the origination message, in step 217, the BS 110detects an available or idle traffic channel, in step 219. If thereexists an idle traffic channel, the BS 110 assigns it to the MS 100, instep 221. However, if there is no idle traffic channel, the BS 110places the MS 100 in the PACA state. Then BS 110, sends a PACA messageto the MS 100, in step 225, while it also sends a channel assign failmessage, “CH_ASSIGN_FAIL” which represents failure in the attempt toassign a traffic channel to the MSC 130, in step 227.

[0008] Meanwhile, the MS 100 receives the PACA display message thatstates, “PACA-State” which informs the user, in step 229, that the MS100 has been shifted to the “PACA-State.” As previously stated, the PACAstate indicates that the BS 110 cannot assign an available trafficchannel, with a communication priority, to the MS 100 because there isno available channel. MS 100 is placed on a standby mode for apredetermined time, for example 1 minute, to periodically re-send theorigination signal, until the BS 110 detects an idle traffic channelassigned to the MS. In this case, the BS 110 determines whether the MS100 has the communication priority or not, based on the subscriber'sinformation of the MS 100 contained in the assign request messagereceived from the MSC 130. Thus, if an idle traffic channel occurs inthe BS 110, the MS 100 is immediately connected to it from the PACAstate to establish a communication channel.

[0009] However, the aforementioned conventional method does not providethe MSC 130 a method to distinguish when the MS 100 has been assigned toa traffic channel during the PACA state from the MS 100 that has beenassigned to a traffic channel through the ordinary assignment process,especially in charging the subscriber. In addition, when the MS 100 ishanded off from one BS to another, the former BS unnecessarily storesthe subscriber's information of the MS 100, thereby increasingconsumption of the resources. Moreover, when the MS 100 re-sends theorigination signal in the PACA state, the subscriber's information isadditionally stored and maintained in the BS, which also increasesconsumption of the resources as in handoff.

[0010] Therefore, a need exists for an apparatus and method that can beutilized to distinguish the MS that has been assigned to a trafficchannel during the PACA state from the MS that has been assigned atraffic channel through an ordinary assignment process. In addition,there exists a need for an apparatus and method that does not store asubscriber's information of a MS.

SUMMARY OF THE INVENTION

[0011] It is an object of the present invention to provide a method forcontrolling a PACA call in a mobile telecommunication system, which maydistinguish the PACA call from the ordinary call in charging thecommunications services.

[0012] It is another object of the present invention to provide a methodfor controlling a PACA call in a mobile telecommunication system, whichmay delete the PACA call information from the BS from which the MS ishanded off to a new BS, thereby improving the storage efficiency of thePACA buffer.

[0013] It is still another object of the present invention to provide amethod for controlling a PACA call in a mobile telecommunication system,which may delete the PACA call information previously stored in the BSwhen the MS in the PACA state, sends a new origination signal which isreceived and stored by the BS.

[0014] It is still another object of the present invention to provide amethod for controlling a PACA call in a mobile telecommunication system,which may delete the PACA call information stored in the BS when the MSdeletes it, thereby improving the storage efficiency of the PACA buffer.

[0015] It is yet another object of the present invention to provide amethod for controlling a PACA call in a mobile telecommunication system,which may send a busy tone signal to a caller who has sent a call signalto the MS in the PACA state without requesting the MS to receive it.

[0016] According to the present invention, a method for controlling aPACA call in a mobile telecommunication system, comprises: sending a neworigination message from a mobile station in the PACA state to a basestation; sending a service request message for the PACA call from thebase station to a mobile switching center; requesting from the mobileswitching center that the base station assign a traffic channel to themobile station; assigning an available traffic channel to the mobilestation to start a communication; and distinguishing the PACA callservice from an ordinary call service.

[0017] The present invention will now be described more specificallywith reference to the drawings attached only by way of example.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The above and other objects, features, and advantages of thepresent invention will become more apparent in light of the followingdetailed description of an exemplary embodiment thereof taken inconjunction with the attached drawings in which:

[0019]FIG. 1 illustrates a schematic diagram that depicts the structureof a conventional mobile communication system;

[0020]FIG. 2 illustrates a flow diagram that depicts the process ofshifting an MS to the PACA state, according to the conventional method;

[0021]FIG. 3 illustrates a flow diagram that depicts shifting an MS tothe PACA state and assigning a traffic channel thereto, according to thepresent invention;

[0022]FIG. 4 illustrates a flow diagram that depicts updating the PACAcall information of the MSC, according to the present invention;

[0023]FIG. 5 illustrates a flow diagram that depicts handing off thePACA call, according to the present invention;

[0024]FIG. 6 illustrates a flow diagram that depicts sending areorigination message for the PACA call;

[0025]FIG. 7 illustrates a flow diagram that depicts canceling the PACAcall, according to the present invention; and

[0026]FIG. 8 illustrates a flow diagram that depicts controlling a callsignal directed toward the MS in the PACA state, according to thepresent invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0027] Throughout the description, in connection with the drawings,there are omitted detailed descriptions of the conventional parts notrequired to comprehend the technical concept of the present invention.The terms used in this specification are only to help understanddescriptions of the essential functions connected with the invention,and should be interpreted based on the meaning the whole specificationintends to convey including the attached claims.

[0028] Hereinafter described is the inventive system of controlling aPACA call in connection with FIGS. 1 and 3 to 7. There is a descriptionof the first process of shifting an MS to the, PACA state “PACA_STATE”and assigning a traffic channel thereto with reference to FIG. 3. e MS100 is requested by the user to send a signal, in step 311, then itsends the signal in the form of an origination message to a BS 110, instep 313. Then, the BS 110 sends an acknowledge order message,“BS_ACK_ORDER_MSG” to the MS 100, in step 315, and a communicationservice request message “CM_SERVICE_REQ” to the MSC 130, in step 317.The MSC 130 sends a subscriber's information request message“MS_CgVSvcingRQ_Msg” to the HLR 140/VLR (not shown) to request thesubscriber's information of the MS 100, in step 319. The HLR/VLRretrieves the subscriber's information loaded on a subscriber'sinformation response message, “MS_CgVSvcing” (PACA call flag) deliveredto the MSC 130, in step 321.

[0029] In this case, the subscriber's information response messagecontains states, “PACA_Call_flag” which is set to have a predeterminedvalue, for example 1 if the MS has priority for the PACA call. The MSC130 receives the subscriber's information response message, then sends achannel assign request message, “ASSIGNMENT_REQ” to request the BS 110assign a traffic channel to the MS 100, in step 323. The channel assignrequest message contains “queuing allowed” information to allow the PACAcall because the subscriber's information represents priority for thePACA call. Then, the BS 110 detects, in step 325, if there is anavailable or idle traffic channel to be assigned to the MS 100 to have anormal communication, in step 327.

[0030] In this case, if there is no idle traffic channel, the BS 110places the MS 100 in the PACA state “PACA_STATE,” in step 329, thensends a channel assign fail message “Assignment_Fail” to the MSC 130, instep 331. The channel assign fail message states “PACA call queued”information, which shows that the MS 100 has been shifted to the PACAstate “PACA_STATE,” where information is stored in the PACA buffer ofthe BS 110. Although, not shown, the MSC 130 notifies the HLR 140/VLRthat the MS 100 is in the, PACA state “PACA_STATE.” Meanwhile, the BS110 stores the PACA call of the MS 100 in the PACA buffer, sending, instep 333, a PACA call storage message to the MS 100, which representsthe address, for example, “00000” of the PACA call queue message storedin the PACA buffer. Whenever the address of the PACA call queue ischanged, the BS 110 sends the PACA call storage message to inform the MS100 of the changed address, for example “00001”, in step 335.Subsequently, if the BS 110 detects an idle traffic channel, in step337, the MS 100 is notified of it. Then, the MS 100 sends, in step 339,the reorigination message to the BS 110, which in turn sends acommunication service request message “CM_SERVICE_REQ” to the MSC 130,in step 341. In this case, the communication service request messagecontains the PACA reorigination indicator “PACA_REORIG”,which indicatesthat the reorigination message is a PACA call. The MSC 130, sends instep 343, the subscriber's information request message to the HLR14O/VLR, which, in turn, sends the subscriber's information responsemessage to the MSC 130. Receiving the subscriber's information responsemessage, the MSC 130 sends, in step 347, the channel assign requestmessage to the BS 110 to assign a traffic channel for the reoriginationmessage to the MS 100 in step 349. Then, the BS 110 sends the channelassignment message, “Channel_Assignment,” in step 351. After the MS 100has completed communication, the MSC 130 distinguishes the PACA callservice from the ordinary call service in charging the subscriber basedon the PACA reorigination indicator “PACA_REORIG” contained in thereorigination message.

[0031] The process of updating the PACA call in the MSC is described inconnection with FIG. 4. Receiving an origination message, in step 411,the MSC 130 determines, in step 413, whether the origination message isthe PACA call or not. If not, the MSC 130 treats it as the ordinary callin step 415.

[0032] However, if the origination message is indicative of the PACAcall, then the MSC 130 requests the HLR 14O/VLR to send the subscriber'sinformation of the origination message, which is analyzed to determine,in step 417, whether the subscriber's registered location of theorigination message agrees with the registration of the HLR/VLR or not.If they do not agree, the MSC 130 determines if the MS 100 has beenhanded off from the previous BS to a new BS, then sends a first PACAcall update message to the previous BS. The first PACA call updatemessage requests the previous BS delete the PACA call information fromthe PACA buffer because the previous BS need not deal with it. Theprocess of dealing with the PACA call concerning the handoff of the MS100 will be described in connection with FIG. 5.

[0033] Meanwhile, if the subscriber's registered location of theorigination message agrees with the origination message registered inHLR/VLR, then the MSC 130 determines whether the MS 100 is enabled forthe “PACA_STATE” in HLR 140/VLR, in step 421. If the MS is enabled forthe PACA state, the MSC 130 determines, in step 423, whether the cell IDof the origination message agrees with the origination messageregistered in HLR/VLR. If they agree, the MSC 130 determines that the MShas sent a new origination message in the PACA state, then sends asecond PACA call update message to the base station in step 425. Thesecond PACA call update message requests the BS 110 delete the previousPACA call stored in the PACA buffer because of the new originationmessage. The process of dealing with the new PACA call generated fromthe MS 100 in the PACA state “PACA_STATE” will be described inconnection with FIG. 6.

[0034] Referring to FIG. 5 there is a description of the process ofdealing with the PACA call concerning the handoff of the MS 100 inconnection with FIG. 5. The MS 100 sends the origination message to thefirst BS on request by the user, in step 511. Then, the first BS sendsthe BS acknowledge order message to the MS 100, in step 513, and thecommunication service request message to the MSC 130, in step 515. TheMSC 130, sends, in step 517, the subscriber's information requestmessage to HLR 14O/VLR to 30 retrieve the subscriber's information ofthe MS 100. The HLR/VLR loads the retrieved subscriber's information onthe subscriber's information response message delivered to the MSC 130,in step 519. The subscriber's information response message,“PACA_Call_flag” is set to have a predetermined value, for example 1 ifthe MS has priority for the PACA call.

[0035] The MSC 130 receives the subscriber's information responsemessage, then sends a channel assign request message to request thefirst BS 110 to assign a traffic channel to the MS, in step 521. Thechannel assign request message contains “queuing allowed” information toallow the PACA call, because the subscriber's information of the MS 100represents priority for the PACA call. Then, the first BS 110 detects anavailable or idle traffic channel. If there is no idle traffic channel,the first BS determines that the MS 100 is in the PACA state“PACA_STATE,” which indicates the storage of the origination message ofthe MS 100 as the PACA call in the PACA buffer. The PACA call is sent asa storage message that represents the address of the PACA call queue inthe PACA buffer, for example “00000” to the MS 100, in step 523. Inaddition, the first BS sends the channel assign fail message to the MSC130, in step 525. The channel assign fail message contains the PACA callqueued information representing that the PACA state of the MS 100 hasbeen stored in the PACA buffer of the BS 110. Subsequently, the MSC 130receives the channel assign fail message, then sends the MS aninformation update message, “MS_CallReleaseRP PACA_STATE,” to VLR toupdate the information of the MS. The MS information update messagecontains the information representing that the MS 100 has been shiftedto the PACA state “PACA_STATE” stored in the PACA buffer.

[0036] Meanwhile, if the MS 100 is handed off from the previous BS(hereinafter referred to as “first BS”) to another BS (hereinafterreferred to as “second BS”), in step 529, it sends a new originationmessage containing the PACA reorigination indicator “PACA_REORIG” to thesecond BS, in step 531. Then, the second BS sends the BS acknowledgeorder message to the MS 100, in step 533, and the communication requestmessage including the PACA reorigination indicator to the MSC 130, instep 535. The MSC 130, in turn, sends the subscriber's informationrequest message to the VLR to provide the subscriber's information ofthe MS 100, in step 537. Then the VLR retrieves the subscriber'sinformation loaded on the subscriber's information response messagedelivered to the MSC 130, in step 539. In this case, the subscriber'sinformation response message includes both the status information of theMS 100 being in the PACA state and the location information of the MS100 registered in the VLR.

[0037] Then the MSC 130 sends a first PACA update message to the firstBS, in step 541. The first PACA update message is the message requestingthe first BS to delete the PACA call stored in the PACA buffer of thefirst BS because the MS 100 has been handed off from the first to thesecond BS. Hence, the first BS sends the PACA update response message tothe MS after deleting the PACA call from the PACA buffer, in step 543.Then, the MSC 130 sends the channel assign request message to the secondBS to assign a traffic channel, in step 545. The second BS sends thechannel assign message to notify the MS 100 that a traffic channel hasbeen assigned to it, in step 547, so that the MS 100 performs anordinary communication, in step 549. Terminating the communication, theMSC 130 sends the information update message of the MS to the VLR todelete the PACA state information of the MS 100, in step 551.

[0038] Referring to FIG. 6, there is a description of the process ofmanaging the PACA call when the MS 100 sends a new PACA call in the PACAstate “PACA_STATE.” If the MS 100, while being in the PACA state, instep 611, sends a new origination message containing the PACAreorigination indicator, “PACA_REORIG” to the BS 110, in step 613, thenthe BS 110 sends the BS response order message to the MS 100, in step615. Then, the BS 110 sends the communication service request messagecontaining the, “PACA_REORIG” indicator to the MSC 130, in step 617, sothat the MSC 130 sends, in step 619, the subscriber's informationrequest message to the VLR to obtain the subscriber's information. TheVLR retrieves the requested subscriber's information loaded on thesubscriber's information response message delivered to the MSC, in step621. In this case, the subscriber's information response messageincludes both the status information of the MS 100 being in the PACAstate and the location information of the MS 100 registered in the VLR.

[0039] Then the MSC 130 sends a second PACA update message to the BS110, in step 623. The second PACA update message is the messagerequesting the BS to delete the previous PACA call stored in the PACAbuffer of the BS because the MS 100 has sent the new origination messagerequesting again the PACA call. Hence, the BS 110 sends the PACA updateresponse message to the MS 130 after deleting the previous PACA callfrom the PACA buffer, in step 625. Then, the MSC 130 sends the channelassign request message to the BS 110 to assign a traffic channel, instep 627. Then, the BS 110 detects an available traffic channel toassign to the MS. If BS 110 does not detect an available trafficchannel, then the BS 110 stores the PACA call into the PACA buffer,sending, in step 629, the channel assign fail message containing thePACA call queued information to the MSC 130. The MSC 130 sends the PACAcall update message to the VLR to update the PACA state of the MS 100,in step 631. In addition, the BS 110 sends the PACA storage messagecontaining the PACA call state representing the storage location of thePACA call in the PACA buffer to the MS 100, in step 633.

[0040] Describing the process of canceling the PACA call in connectionwith FIG. 7, the MS 100 detects the PACA call cancellation entered bythe user, in step 711. If MS 100 detects the PACA call cancellationentered by the user, then the MS sends the PACA cancellation message tothe BS 110 in step 713, so that the BS 110 sends the BS response ordermessage to the MS 100, in step 715, which deletes the PACA call from thePACA buffer. The PACA update message, indicates that the MS 100 has beenreleased from the PACA state to the MSC 130, in step 717. Then, the MSC130 sends, in step 719, the MS PACA update message “MS_PACAUpdateRP,”indicates that the MS 100 has been released from the PACA state to theVLR, and the PACA update response message to the BS 110, in step 721. Ofcourse, the PACA call may also be cancelled by the BS 110. Referring toFIG. 8, there is a description of the process of warding off a call fromthe MS in the PACA state in connection with FIG. 8. The MSC 130retrieves the receiving subscriber's information of the call detected,in step 811, to analyze it, in step 813, thereby determining, in step815, whether the receiving subscriber is in the PACA state or not. Ifthe receiving subscriber is in the PACA state, the MS 130 sends the busytone to the subscriber requesting the call, in step 817. Alternatively,if the receiving subscriber is not in the PACA state, the MSC 130 sendsa paging message to the BS 110 registering the receiving subscriber, instep 819, which in turn transfers it to the MS 100, in step 821. Then,the MS 100 sends the paging response message to the BS 110 in step 823,which in turn transfers it to the MSC 130,in step 825. Then, the MSC 130sends the channel assign request message to the BS 110, in step 827, sothat the BS 110 assigns, in step 829, a traffic channel to the MS 100shifted to the communication stated, in step 831.

[0041] Thus, the present invention provides a mobile telecommunicationsystem with means to distinguish the PACA call from the ordinary call incharging the communications services. In addition, the present inventiondeletes the PACA call information from the BS when the MS is handed offto a new BS or when the MS in the PACA state. Then, the presentinvention sends a new origination signal or when the MS BS cancels thePACA call, thereby improving the storage efficiency of the PACA buffer.Further, the present invention sends the busy tone signal to a callerwho has sent a call signal to the MS in the PACA state withoutrequesting the MS to receive it.

[0042] While the present invention has been described in connection withspecific embodiments accompanied by the attached drawings, it will bereadily apparent to those skilled in the art that various changes andmodifications may be made thereto without departing from the gist of thepresent invention.

What is claimed is:
 1. A method for controlling a priority access andchannel assignment (PACA) call in a mobile telecommunication system, themethod comprising: sending a new origination message from a mobilestation in a PACA state to a base station; sending a service requestmessage for the PACA call from the base station to a mobile switchingcenter; requesting from the mobile switching center that the basestation assign a traffic channel to the mobile station; assigning anavailable traffic channel to the mobile station to start acommunication; and distinguishing the PACA call service from an ordinarycall service.
 2. A method as defined in claim 1 , wherein the neworigination message includes a parameter for indicating that that thePACA call is requested again.
 3. A method as defined in claim 1 ,wherein the available traffic channel is assigned to the mobile stationto start a communication by the base station.
 4. A method as defined inclaim 1 , wherein the PACA call service is distinguished from theordinary call service by the mobile switching center.
 5. A method forcontrolling a PACA call in a mobile telecommunication system, the methodcomprising: determining whether or not an origination message from amobile station for the PACA call has the same subscriber's registeredlocation as the subscriber's registered location in a visitor locationregister (VLR); determining that the mobile station has been handed offfrom a previous base station to a new base station if the subscriber'sregistered location of the origination message is not the same as thatof the VLR; sending a first PACA call update message to the previousbase station; and deleting the first PACA call information from theprevious base station.
 6. A method as defined in claim 5 , wherein thedeleted first PACA call information is stored in a PACA call buffer ofthe previous base station.
 7. A method as defined in claim 5 , whereinthe subscriber's location registered in the VLR is registered when themobile station is shifted to a PACA state after sending the originationmessage.
 8. A method as defined in claim 5 , wherein the originationmessage is determined as the PACA call by detecting a parameterrepresenting the PACA call.
 9. A method as defined in claim 8 , furthercomprising: determining whether the mobile station is in the PACA stateor not, if the subscriber's registered location of the originationmessage does not agree with that of the VLR; determining whether a cellID of the origination message agrees with the origination messageregistered in the VLR if the mobile station is in the PACA state;determining that the mobile station has sent a new origination messagein the PACA state if the cell ID of the origination message agrees withthat registered in the VLR; sending a second PACA call update message tothe previous base station; and deleting the second PACA call informationfrom the previous base station.
 10. A method as defined in claim 9 ,wherein the PACA call deleted from the base station is previously storedin the PACA call buffer of the base station.
 11. A method forcontrolling a PACA call in a mobile telecommunication system, the methodcomprising: sending a PACA call cancel message from a mobile station ina PACA state to a base station; sending a PACA call update message fromthe base station to a mobile switching center; and sending a mobilestation PACA CALL update message from the mobile switching center to theVLR.
 12. A method as defined in claim 11 , further comprising deletingthe PACA call update message from the mobile station.
 13. A method forcontrolling a PACA call in a mobile telecommunication system, the methodcomprising: analyzing information from a receiving subscriber towardwhich a call signal is directed; and canceling the call signal when amobile station of the receiving subscriber is in a PACA state.
 14. Amethod as defined in claim 13 , further comprising sending a busy toneto a sending subscriber who has generated the call signal.
 15. A methodas defined in claim 13 , further comprising sending a call message tothe mobile station of the receiving subscriber when it is not in thePACA state.
 16. A system for controlling a priority access and channelassignment (PACA) call in a mobile telecommunication system, the systemcomprising: a mobile station configured to send a new originationmessage in a PACA state to a base station; the base station configuredto send a service request message for the PACA call to a mobileswitching center; the mobile switching center configured to request thebase station to assign a traffic channel to the mobile station; the basestation further configured to assign an available traffic channel to themobile station to start a communication; and the mobile switching centerfurther configured to distinguish the PACA call from an ordinary callservice.
 17. An apparatus for controlling a priority access and channelassignment (PACA) call in a mobile telecommunication system, theapparatus comprising: a mobile switching center configured todistinguish a PACA call from an ordinary call service.